This invention relates in general to burner units and, more particularly, to burner units which are capable of reducing undesired particulate and gaseous emissions.
The term "burner unit" as used herein refers to a combustor assembly which combines two separate flow streams, namely, a gaseous fuel flow stream and an oxidizer flow stream for combustion purposes. Typical burner units employed in industrial applications today often mix fuel and oxidizer at relatively high velocities. This high velocity mixing technique frequently results in several undesired problems such as increased burner wear and damage, low efficiency, high pollutant production and added maintenance.
Modern approaches to the reduction of pollutant emissions in combustion processes have involved the use of oxygen enrichment. In many cases the increased operating temperatures which result from the increased oxygen content in the oxidizer actually cause an increase in undesired NOX production. The high fuel-oxidizer mixing velocities found in contemporary burners also contribute to high particulate entrainment and high temperature operation. It is noted that these high burner operating temperatures are a significant cause of oxygen-related pollution such as NOX. In oxygen enriched combustion processes using conventional burners, high flame temperatures result in high NOX pollution production because nitrogen which remains after combustion may still react with available oxygen to form undesired NOX compounds at very high rates.
Conventional high temperature burners which operate in an oxygen enriched environment require special materials to enable high temperature operation. Alternatively, these high temperature burners employ extra external cooling to prevent damage to the burner. In either case, the burner unit is made significantly more expensive to enable high temperature operation.